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Monday, October 10, 2011

AEGs, AEPs, and Hop Up

AEGs are by far the most
popular high quality Airsoft guns and their introduction in the 1990’s
completely changed the face of Airsoft forever. The revolutionary design
allowed Airsoft guns to be fired without the help of gas, with a higher ROF
(Rate Of Fire), in more weather conditions, more reliably, and be produced for
less. Without AEGs, Airsoft as we know it today probably wouldn’t exist,
especially in non-Asian countries.

AEG stands for Automatic Electric Gun. AEGs operate on battery power to fire plastic BBs at high rates
of fire. It all starts with the battery. These vary in size and even type, but
most Airsoft batteries are 8.4V NiMH (Nickel-Metal Hydride) batteries. Some
other batteries include NiCD (Nickel-Cadmium) and Li-Po (Lithium-Polymer).
Airsoft batteries vary in voltage, but are usually somewhere between 7V and 12V
regardless of battery style. The battery is connected by wires to a motor,
which is usually in the pistol grip of the rifle. There three different styles
of motors and basically every Airsoft gun manufacturer makes their own version.
This motor has a gear on the end of it, which penetrates in to the gearbox and
spins its gear assembly. Generally the gear assembly inside the gear box consists
of only three gears: the bevel gear, the spur gear, and the sector gear. All
these gears must be shimmed properly or bad things will happen. In front of the
gears are the trigger and trigger switch, and some wiring. Above the gears
there is a cylinder which contains a piston. The piston is on a tight spring,
and the cylinder is capped off with a cylinder head. On the end of the cylinder
head is a small air nozzle, which is connected to the tappet plate, which rests
on top of the sector gear. Phew!

When you pull the
trigger the motor starts the bevel gear spinning, which in turn causes the spur
gear and then the sector gear to spin. The sector gear does two important
things. Firstly, it pulls back the piston which compresses the spring. A small
metal nub on the sector gear also pulls back the tappet plate. When the tappet
plate comes back, so does the air nozzle. The air nozzle covers the feeding
tube that the BBs are being pushed up by a spring in the gun’s magazine. The
air nozzle comes back and a BB chambers. Meanwhile, the sector gear rotates to
a point where its teeth are no longer holding the piston back in place. The
spring tension now causes the piston to shoot forward, creating a burst of air
that travels through the cylinder head and the air nozzle. This burst of air
fires the BB, and the process is repeated again. When firing in full auto, this
all happens multiple times a second. That’s pretty impressive if you ask me.
Regardless of what model of gun you have, or what company it came from, the basic
operation will almost always be the same.

Hop up is a very basic
concept. It is simply a rubber nub that protrudes partially from the top of the
barrel. When you adjust the hop up, all it does is make this nub extend farther
or less far in to the barrel. When the BB fires it catches on this nub, which
puts a backspin on the BB. This makes the BBs go much farther when adjusted
properly, but if it is set too high then the BBs will curve up when fired or it
might even block the barrel and then they won’t fire at all. To properly adjust
you simply fire a BB and see if it shoots downwards, upwards, or straight. If
the gun is shooting BBs down or not very far, turn up the hop up system. If
they are curving up, turn the hop up system down. Hop up adjustments can
usually be made by pulling back the gun’s slide and rotating a gear. Some hop
up systems are adjusted differently but the owner’s manual always point out
where the adjustment point is.

In recent years there
have been new guns on the market called AEPs (Automatic Electric Pistols).
These are handguns and small submachine guns that operate on a scaled-down
version of the Tokyo Marui AEG system. Because of the smaller components they
aren’t quite as powerful as AEGs, and there is less room for upgrades. However,
they are more efficient and consistent than the gas powered pistols that were
the standard before AEPs came along. They are also less affected by weather,
gas powered pistols basically don’t work in really cold temperatures. AEPs
currently only fire in the 200-300 FPS range, which isn’t incredibly powerful,
but is fine for a side arm. They are much more powerful than EBB pistols, which
are the only other battery powered handgun option.

Now you have a basic
understanding of how AEGs work. In fact, you pretty much understand the entire
operation, except for the wiring and trigger switch, a couple other small
things. AEGs aren’t terribly complicated machines, and they are pretty easy to
work on. However I suggest that you don’t open up your own gearbox unless you
are with a friend that knows what they are doing. There are certain components,
like the anti-reversal latch (a small latch that prevents the gears from
spinning backwards), that have springs on them or have to go in just the right
way. If you place these components in at the wrong angle, or with the spring
attached incorrectly, catastrophic failure can happen and you’ll end up
breaking a bunch of teeth on your gears and all sorts of bad things will
happen. The gears also need to be shimmed perfectly, and you’ll probably end up
losing track of where all the shims were supposed to go, and then it can
literally take hours to get it set up properly again, especially if you don’t
know what you are doing. If you want to replace a spring or a piston, that is
fairly easy, and you can do it without touching the gear assembly or any of the
more complicated parts. It also isn’t very hard to find gearboxes, if you look
around you can probably find a used one and pick it up for twenty or thirty
dollars, and then you can have a gearbox just for learning on, as well as extra
parts in case you need them. Be aware that if you do open the gearbox, there is
a highly compressed spring inside there. You need to stick a thin screwdriver
through the hole in the rear of the gearbox, to release spring tension with
once the gearbox is open. Do this at your own risk, and wear some shop glasses.
I hope you’ve learned something today. So head on over to HobbyTron and
I’ll see you on the field.